Metaclisa (Trichometaclisa), Nabozhenko & Mckellar & Bukejs, 2021

Nabozhenko, Maxim V., Mckellar, Ryan C. & Bukejs, Andris, 2021, The first described darkling beetle of the tribe Metaclisini (Coleoptera: Tenebrionidae) from Eocene Baltic amber, Zootaxa 4999 (3), pp. 279-284 : 280

Subgenus Trichometaclisa subgen. nov.

Type species: Metaclisa ottoi sp. nov., by present designation.

Diagnosis. The type species of the new subgenus differs from all known Metaclisini in the presence of short, fine recumbent setation on dorsal surface (at least on pronotum and elytra); this is a significant difference from all known extant Metaclisa (body dorsally glabrous), and the new species is further distinguished by flattened lateral sides of the pronotum. In addition, the prosternal process in Metaclisa ottoi sp. nov. is roundly bent down and weakly projecting posterior to procoxae, in contrast to extant species.

Etymology. “ Tricho -“ prefix comes from Greek thrix, trikhos for “hair”, and is combined with Metaclisa , type genus for the tribe. Gender feminine.

Notes. The taxonomic placement of the studied species within the family Tenebrionidae is based on the following combination of features: tarsal formula 5-5-4, antennae 11-segmented, genae conceal base of antennomere 1, five abdominal ventrites with intersegmental membranes between ventrites 3–5 (tenebrionoid lineage of the family). The specimen is externally very similar to genera of the tribe Alphitobiini Reitter, 1917 , especially Alphitopsis initialis Kirejtshuk, Nabozhenko & Nel, 2011 (extinct, Early Cretaceous), Alphitobius Stephens, 1829 (extant) and Diaclina Jacquelin du Val, 1861 (extant). However, it can be distinguished from these genera based upon the following characters, which have been indicated partly by Kirejtshuk et al. (2011) and completely by Steiner (2016) for Metaclisa : basal tarsomeres ventrally bear dense pads of fine golden setae, not arranged in two rows; the first (epipleural) elytral punctate stria tapers to end before the elytral apex and does not join the sutural stria at the apex; and epipleura ending before elytral apex (only this character of the three listed is visible on the compression fossil of Alphitopsis ). The combination of other external characters also corresponds to the diagnosis of the tribe Metaclisini ( Steiner 2016) . The elytral setation of Metaclisa ottoi is an unusual character for Metaclisini , but we believe that only this one character is not enough to give a genus rank to a new taxon. Metaclisa ottoi additionally differs from extinct Alphitopsis initialis base upon the structure of its antennae (antennomeres 6–10 possess a stick-shaped base in Alphitopsis ).